CN1337788A - Echo-eliminating method and apparatus thereof - Google Patents

Abstract

The echo canceling device has an echo canceller for canceling the leaked speech signal of the part of the speech signal passing through the speech receiving path to the speech sending path. The echo canceling device further includes an input level adjustment unit for limiting the level of the transmitted voice signal input to the echo canceller to a value within a predetermined range, and an electrical level adjustment unit for controlling the transmitted voice signal output from the echo canceller. level, an output level adjustment unit that returns to the level before being limited by the input level adjustment unit. Thus, even if the level of the voice signal in the transmission path changes due to network level design, hybrid circuit characteristics that cause echo, etc., echo cancellation can always be properly performed.

Description

Echo cancellation method and echo cancellation device

technical field

The present invention relates to an echo canceling method and an echo canceling device, which are used for canceling the leaked voice signal caused by a part of the receiving voice signal mixed into the sending voice signal in communication equipment such as a telephone communication system.

Background technique

In voice networks such as telephones, due to acoustic feedback and other reasons, it is possible that part of the receiving signal may be mixed into the sending signal in the hybrid circuit used for the mutual conversion between the four-wire circuit and the two-wire circuit and in the terminal device of the end user. internal echo phenomenon. The combination of this echo and network delay is responsible for the degradation of voice quality. Therefore, in voice transmission devices that add voice signals to ATM (Asynchronous Transfer Mode) units or IP (Internet Protocol: Internet Protocol) packets, etc., echo cancellation devices are generally equipped to prevent low voice quality. .

A conventional echo canceller of this type is disclosed, for example, in JP-A-8-130497. This echo canceling device first carries out the judgment of the single-talk state in which the voice signal is only transmitted in the receiving path, and the double-talking state transmitted in both the sending path and the receiving path, and then only the echo path in the single-talking state features are inferred.

The above-mentioned existing echo canceling device uses multiple parameters when judging the single-talk state and the double-talk state. flat parameters. Therefore, due to the design of the network level and the characteristics of the hybrid circuit that causes the echo, it is easy to make a misjudgment in any state of double-talk or single-talk, which makes it impossible to perform a reasonable cancellation operation at certain times. This should be resolved one question.

Contents of the invention

The present invention is to solve the problems of the above-mentioned prior art, and the purpose is to provide a method that can perform reasonable echo at any time even if the level of the voice signal of the transmission channel changes due to the design of the network level and the characteristics of the hybrid circuit. An echo canceling method and an echo canceling device for canceling operation.

According to one aspect of the present invention, an echo cancellation method can be provided, which is used to eliminate the leaked voice signal of a part of the voice signal passing through the receiving channel leaking to the transmitting channel. This echo canceling method is characterized in that the level of the transmitted voice signal before the leakage voice signal canceling operation is limited to a value within a predetermined range, and the leaked voice signal included in the transmitted voice signal is eliminated. , and then restore the level of the transmitted voice signal after the leaked voice signal elimination operation to the level of the transmitted voice signal before the limited range. In this way, even if the voice signal level of the transmission path changes with the design of the network level and the characteristics of the hybrid circuit that causes echo, echo cancellation can be performed within the appropriate range of the voice signal level. Therefore, echo cancellation is often safe.

It is preferred to monitor the voice transmission channel to determine whether the communication of the fax or the modem is detected, and if it is determined that the communication of the fax or the modem is detected, the elimination operation of the leaked voice signal is terminated, and the operation before the elimination is performed. The limit operation of the transmitted voice signal level, and the recovery operation of the canceled voice signal level. In this way, it is possible to prevent influence on facsimile communication and modem communication accompanied by level adjustment.

In addition, according to another aspect of the present invention, an echo canceller having an echo canceller is provided for canceling a leaked voice signal from a part of the voice signal passing through the receiving channel leaking to the transmitting channel. This echo canceller is characterized in that it has an echo canceller input level adjustment unit that limits the level of the transmitted voice signal input to the echo canceller to a value within a predetermined range, and the echo canceller The echo canceller output level adjustment unit restores the output speech signal level to the original level before being limited by the echo canceller input level adjustment unit. In this way, even if the voice signal level of the transmission path changes depending on the design of the network level and the characteristics of the hybrid circuit that causes echo, echo cancellation can be performed within an appropriate range of the voice signal level. Therefore, echo cancellation is often safe.

Preferably, a judging unit is used to monitor the transmission channel to judge whether the communication of the facsimile or the modem is detected; , terminating the operation of the echo canceller, and simultaneously terminating the level adjustment operations of the echo canceller input level adjustment unit and the echo canceler output level adjustment unit. In this way, it is possible to prevent influence on facsimile communication and modem communication accompanied by level adjustment.

Description of drawings

Fig. 1 shows a structural block diagram of a specific embodiment of an echo cancellation device related to the present invention.

Detailed ways

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 shows a structural block diagram of a specific embodiment of an echo cancellation device related to the present invention.

In the figure, the echo canceller 1 is connected together in a four-terminal structure between the transmitting channel and the receiving channel. In this echo canceling device 1 , the input and output terminals of the voice signal of the receiving channel are connected to each other, and the voice receiving channel is connected with the input terminal of the voice signal of the receiving voice signal of the echo canceller 2 .

The input end of the speech voice signal of the echo canceller 2 is connected with the speech signal input end of the echo canceller 1 through the echo canceller input level adjustment unit 3, and the speech speech signal of the echo canceller 2 The signal output terminal is connected to the voice signal output terminal of the echo canceller 1 through the output level adjustment unit 4 of the echo canceller.

In addition, the voice signal input terminal of the echo canceling device 1 is connected to a fax (hereinafter referred to as FAX)/modem (MODEM: modem) detection unit 5, and its output terminal is connected to the echo canceller 2 and the input circuit of the echo canceller. The control input ends of the level adjustment unit 3 and the echo canceller output level adjustment unit 4 are connected.

Here, the echo canceller 2 is configured to use the received speech output speech signal to perform an operation of canceling the echo of the received speech output speech signal superimposed on the transmitted speech input speech signal.

The echo canceller input level adjustment unit 3 is configured to adjust the level of the transmitted input voice signal received by the echo canceller 1 . For the echo canceller input level adjustment unit 3, an appropriate predetermined level adjustment amount is fixedly set in advance according to the network in which the echo canceler 1 is used. Specifically, in the pre-test process when the echo canceller 1 is applied to the network, the level adjustment amount for the reasonable operation of the echo canceler 2 is experimentally obtained, and the level adjustment amount is set as a fixed value Certainly.

The echo canceller output level adjusting unit 4 is configured to adjust and output the level of the echo-canceled voice output voice signal to the voice channel. In this echo canceller output level adjustment unit 4, an appropriate predetermined level adjustment amount is fixedly set in advance in the same manner as above.

The level adjustment amounts of the echo canceller input level adjustment unit 3 and the echo canceler output level adjustment unit 4 can also be set independently of each other. However, generally speaking, when designing the network level diagram, the level of the echo canceller is not changed, but the level adjustment is performed in other network equipment.

Therefore, in this embodiment, in order to use the echo canceller output level adjustment unit 4 to adjust the level lowered by the echo canceller input level adjustment unit 3 back to the original input level, both sides are set. level adjustment amount. In this way, only the level of the speech input speech signal flowing to the echo canceller 2 can be adjusted without changing the level between the speech input speech signal and the speech output speech signal of the echo canceller 1 . Therefore, even if the echo canceling device 1 is additionally installed on an existing network, there is no need to adjust the level diagrams already set by other network devices, thereby improving its versatility.

In addition, the FAX/modem detection unit 5 has a structure for detecting FAX or modem communication from the transmitted input voice signal, and performing the echo canceller 2, the echo canceller input level adjustment unit 3, and the echo canceller output Level adjustment unit 4 control.

Next, the operation of the echo canceling device having the above-mentioned structure will be described.

The hybrid circuit used in the conversion between the four-wire circuit and the two-wire circuit and the acoustic feedback on the end user's terminal become the cause, so a part of the voice signal output by the echo canceller 1 is superimposed on the voice input An echo is formed on the voice signal and is input to the echo canceller 2 . In the echo canceller 2, the impulse response of the echo path is inferred from the output voice signal of the receiver and the input voice signal of the transmitter, and the output voice signal and the impulse response of the receiver are convoluted to make a simulated echo. The simulated echo is subtracted from the input speech signal to eliminate the echo.

When the echo canceller 2 estimates the impulse response of the echo path, it cannot estimate the impulse response correctly because the input voice signal for transmission contains interference signals in the double-talk state. Therefore, the echo canceller 2 is based on the received speech input voice and the transmitted speech input speech to determine the state of single-talk and double-talk in the network, and only implements the estimation of the echo path impulse response in the single-talk state, and in the Estimation of the stopping impulse response in the double-talk state.

A plurality of parameters are used to determine the state of single-talk and double-talk in the network, and these parameters also include an absolute level parameter of the transmitted input voice signal that depends on the echo canceller 2 . Therefore, due to the design of the network level and the characteristics of the hybrid circuit that causes the echo, etc., even if the absolute level of the transmission input voice signal is relatively high, the impulse response of the echo path can be correctly estimated. But at the same time, it tends to be easily judged as a double talk state. If, once it is judged as a double-talk state in this case, the accuracy of echo cancellation amount and cancellation convergence time will be low.

In this case, in this embodiment, the echo canceller input level adjustment unit 3 is used to lower the level of the transmitted input voice signal flowing to the echo canceller 1 to a level within a specified range, Wave Canceller 2 Input. In this way, the level of the speech input speech signal flowing to the echo canceller 2 can be set within a range in which the echo canceller 2 can appropriately determine the single-talk state and the double-talk state.

The level amount lowered by the echo canceller input level adjustment unit 3 is adjusted up again by the echo canceller output level adjustment unit 4 . Through the echo canceller input level adjustment unit 3 and the echo canceller output level adjustment unit 4, the level can not be changed between the voice input voice signal and the voice output voice signal of the echo canceller 1, and Only the level of the incoming voice signal sent to the echo canceller 2 is adjusted.

In addition, the FAX/modem detection unit 5 monitors the transmission input voice signal flowing to the echo canceller 1, and when it detects that there is FAX communication or modem communication, stops the operation of the echo canceller 2 and stops the echo canceller at the same time. The level adjustment by the input level adjustment unit 3 and the echo canceller output level adjustment unit 4 transparently outputs the speech input speech signal as the speech output speech signal. In this way, it is possible to prevent influence on facsimile communication and modem communication accompanied by level adjustment.

Here, in the above-mentioned embodiment, the case where the level of the transmission input voice signal input to the echo canceling device 1 is relatively high due to the design of the network level and the characteristics of the hybrid circuit which causes the echo, etc. has been described. , but when the speech input voice signal level is relatively low, this echo cancellation method can also be applied, and the echo canceller input level adjustment unit 3 is used to transfer the speech input flow to the echo cancellation device 1 The voice signal level is adjusted to a value within the specified range, and then input to the echo canceller 2, and the output level adjustment unit 4 of the echo canceller is used to adjust the level raised by the input level adjustment unit 3 of the echo canceller again. Just adjust it down.

As can be clearly seen from the above description, according to this embodiment, even if there is a change in the voice signal level of the transmission path due to the design of the network level and the characteristics of the hybrid circuit that cause the echo, the echo can be reduced. The canceller works within the appropriate voice signal level range, and can achieve the effect of obtaining sufficient echo cancellation characteristics in various network environments.

The present invention is not limited to the above-described embodiments, and can be implemented in various forms within the scope of the gist of the present invention described in the appended claims.

Claims (4)

1. A method for echo cancellation, which is used to eliminate the leaked speech signal leaked on the speech path by the part of the speech signal of the receiving path, and is characterized in that it comprises the following steps: a value that limits the level of the transmitted voice signal before said leaked voice signal canceling operation within a prescribed range; canceling the leaky speech signal contained in the spoken speech signal; The level of the transmitted voice signal after the leakage voice signal canceling operation is restored to the level of the transmitted voice signal before the predetermined range is limited. 2. The echo cancellation method as claimed in claim 1, further comprising the steps of: monitoring said transmission path to determine whether a fax or modem communication is detected; If it is determined that the communication of the facsimile or modem is detected, the operation of canceling the leaked voice signal is stopped, the operation of limiting the level of the transmitted voice signal before the cancellation is performed, and the operation of restoring the level of the voice signal after the cancellation is performed. . 3. a kind of echo canceller, this device has the echo canceller that eliminates the leakage speech signal leaked on the speech path by the part speech signal of receiving path, it is characterized in that having: The echo canceller input level adjustment unit is used to limit the level of the transmitted voice signal input to the echo canceller to a value within a specified range; The echo canceller output level adjustment unit is used to restore the level of the speech voice signal output by the echo canceller to the original level before being limited by the echo canceller input level adjustment unit. flat. 4. The echo cancellation device according to claim 3, characterized in that it also has: a judging unit, configured to monitor the transmission path, and judge whether a fax or modem communication is detected; a stop unit, configured to terminate the operation of the echo canceller when it is judged by the judging unit that the communication of the fax or the modem is detected, and simultaneously stop the input level adjustment unit of the echo canceller and the echo canceller. The level adjustment action of the canceller output level adjustment unit.

Images